1. Field of the Invention
The invention relates to a storage system and a path management method, and is suitable for use in, for example, a storage system in which plural hosts connected to the same storage apparatus are provided in a SAN (Storage Area Network) (hereinafter referred to as “multi-host environment”); and the hosts share channel adapters in the storage apparatus, where the channel adapters are interfaces with the hosts.
2. Description of Related Art
In a storage system, when a channel adapter in a storage apparatus, or a controller for controlling the operation of the entire storage apparatus or a micro program that is a control program on the operation control of the storage apparatus is to be replaced, the replacement target has to be stopped temporarily.
Therefore, when no data input/output path for alternation not going through a replacement-target channel adapter or the like and in an online state (hereinafter referred to as “path”) exist between a host and a storage apparatus, the access to a logical volume from the host via a currently-used path is interrupted. This leads to the problem of suspension of operation.
In light of this, the replacement of a channel adapter or similar in a storage apparatus has conventionally needed the following. Before replacing the channel adapter or similar, all the hosts that will be affected by the replacement are identified; the latest management information for each path connected to the hosts (the information on the path's state or route, and hereinafter referred to as “path information”) is acquired; and the path connecting the relevant host to the relevant storage apparatus is changed to an alternate path (one available at this time, i.e., that is in an online state) based on the acquired path information.
JP2005-010956 A discloses a method in which the logical path loads are acquired; and the logical paths to be assigned with data input/output requests are decided according to the loads. US2006-0026346 discloses a method of deciding paths according to resource loads.
However, in a large-scale and complicated multi-path environment, there has been a problem that the above-described identification of the alternate path for the path that goes through the replacement-target channel adapter or similar, requires considerable amounts of labor and time. In addition, after completion of the replacement of the channel adapter or similar, confirmation that all paths affected by the replacement have returned to normal is required. Therefore, there has also been a problem that the confirmation requires considerable amounts of labor and time.
Moreover, there has been a problem that the replacement of the channel adapter or similar requires considerable amounts of labor and time for the reason that the replacement needs to normally take place for each replacement-target, which leads to repetition of the work involved.
Furthermore, when the channel adapter or similar is suspended, software for monitoring the path state erroneously recognizes that a failure has occurred in a path going through the channel adapter or similar. As a result, a warning is displayed on a management server. Therefore, this has been a problem that it is difficult for a storage system administrator to make a judgment as to whether the path is intentionally and temporarily in an error state because the replacement of the channel adapter or similar, or a failure has occurred during actual business operation.